Process for the preparation of glass-concentrate capsules in a polyvinyl chloride matrix

ABSTRACT

Disclosed herein is a process for the preparation of glassconcentrate capsules which comprise a plurality of strands of glass fibers encapsulated in a collimated array within a vinyl chloride polymer matrix which process comprises: 1. Forming a suspension of strands of glass fibers in a vinyl chloride monomer/water mixture containing a critical amount (viz., from 0.05 to 2.0 percent by weight based on the total weight of monomer and glass) of protective colloid; 2. Agitating the suspension using a low-shear type of agitation which moves the whole suspension pass while avoiding localized high-shear agitation; 3. Polymerizing the monomer; and 4. Recovering the glass-concentrate capsules.

United States Patent 1m Baer et a1. [45] Jan. 18, 1972 [54] PROCESS FORTHE PREPARATION OF 3,278,329 10/1966 Wiczer ..117/62 GLASS-CONCENTRATECAPSULES IN A POLYVINYL CHLORIDE MATRIX Massimo Baer, Longmeadow; Joseph0. Campbell, Agawam, both of Mass.

Assignee: Monsanto Company St. Louis, Mo. Filed: Nov. 4, 1969 Appl. No.:873,805

Inventors:

References Cited UNITED STATES PATENTS COATED GLA 5 5 STRAND 5 PrimaryExaminer-Richard D. Lovering Atlorney-William J. Farrington, Arthur E.Hoffman, Neal E. Willis and Richard W. Sternberg [57] ABSTRACT Disclosedherein is a process for the preparation of glass-concentrate capsuleswhich comprise a plurality of strands of glass fibers encapsulated in acollimated array within a vinyl chloride polymer matrix which processcomprises:

1. Forming a suspension of strands of glass fibers in a vinyl chloridemonomer/water mixture containing a critical amount (viz., from 0.05 to2.0 percent by weight based on the total weight of monomer and glass) ofprotective colloid;

2. Agitating the suspension using a low-shear type of agitation whichmoves the whole suspension pass while avoiding localized high-shearagitation;

3. Polymerizing the monomer; and

4. Recovering the glass-concentrate capsules l2 Clalms, 9 DrawlngFlgures PATENTEDJANIBIBYZ 3,635,752

SIZE

GLA 55 STRAND MICROF/BERS GLA55 57/?AND COATED GLA 5 5 STRAND 5 El -4-IE 15:4A COATD GLA55 STRANDfi COATED GLA 5 5 STRANDS INVENTORS MA 5 51M0 BAR JOSEPH O. CAMP5LL BYwLl fimUJ,. ATTORNEY PROCESS FOR THEPREPARATIONOF GLASS CONCEN'I'RATE CAPSULES IN A POLYVINYL CHLORIDEMATRIX BACKGROUND OF THE INVENTION 1 Field of the Invention The presentinvention is directed to a method for the preparation ofglass-concentrate capsules which comprises a plurality of strands ofglass fibers encapsulated in a collimated array within a vinyl chloridepolymer matrix.

2. Description of the Prior Art The use of glass fibers as a reinforcingmedium in thermoplastic resin composites is well known in die prior art.

In the preparation of glass fiber reinforced composites it isconventional to use strands of glass fibers which vary'rn length from1/32 inch to lli inch or longer. These glass strands are conventionallymade up of from 200 to 300 microfibers having a diameter in the order of0.00035 inch which are arranged in a parallel configuration. The surfaceof the glass strand is conventionally coated with a coupling agent and afilm-forming size which keeps the microfibers together and maintains theintegrity of the strand. The glass strands are then dry blended with athermoplastic resin matrix and fed to an extruder or injection moldingmachine wherein the fibers are distributed throughout the resin matrixand serve as reinforcing elements in the finished composite.

Dry-blending of the glass and resin matrix is considered to be thesimplest, most versatile and economical route for largevolumepreparation of composites. However, it involves high capital investmentfor the equipment necessary to avoid the very severe problems ofnonuniformity of glass distribution and segregation, debundling,bridging. haystacking and matting of glass during blending, feeding andprocessing. Consequently, special vibrator proportioning and meteringfeeds are required.

Debundling is the term to describe that occurrence where the glassstrand loses its integrity and the individual microfibers are scattered.Consequently. the loose niicrofibers would undergo bridging or formhaystacking configurations (haystaclring) in the hopper which feeds theextruder or injection molding machine. As a result of this haystacking,the desired feed ratio of glass fibers to resin matrix to the molding orextrusion operation would be upset and an inferior product would beproduced. Alternatively, the haystack would be fed to the machine in thenature of an embolism and would result in matting of the glass fibersand possible clogging of the machinery causing machine breakdown and/orinferior products.

Attempts to solve the problems of debundling and haystacking ledresearchers to coat the glass strand with thermoplastic resin polymers.Bradt, in US. Pat. No. 2,877,501, teaches coating the outside of anendless glass strand with a polymeric coating followed by heat treatmentto fuse the polymer then cutting the strand to the desired lengths. Inthis method, the cut ends of the glass strands contain exposed ends ofmicrofibers and are possible sites for subsequent debundling. Moreover,there is a polymer gradient which decreases toward the center of thestrand. Consequently, the individual microfiber-s in the core of thestrand may not be coated with polymer. Thus, the shearing forces ofinjection molding or extrusion could cause abrasion of the individualmicrofibers in the core of the strand with resulting damage to thesefibers which detracts from their reinforcing ability.

Malinowski et al. in US. Pat. No. 2,688,774, Herman et al. in U.S. Pat.No. 3,265,644; and Wiczer in US. Pat. No. 3,278,329 provide a partialsolution to the problems mentioned above by coating the glass strandwith monomer followed by in situ polymerization to give a single glassstrand contained within a thermoplastic resin capsule. In some instancesthe monomers wet the individual microflbers and upon polymerizationprovide a coating which helped to protect the microfibers from theadverse effects of abrasion during composite preparation.

However, in the foregoing methods, it is not possible to obtain a highconcentration of glass fibers in capsule form which is a desired featurein the preparation of glass-filled composites. Moreover, in manyinstances the capsules of the prior art, which contain a single glassstrand, rather than a plurality of collimated glass strands, have adifferent density, size and shape than the particles of resin matrixbeing fed to the extruder or molding apparatus. These differences mayresult in segregating of the respective particles and a nonuniformproduct.

Moreover, the glass fibers of the prior art have been mainly used toreinforce polymers such as polystyrene, poly(styrene/acrylonitrile)copolymers, polyesters, etc. Only limited success has been obtained intrying to reinforce poly( vinyl chloride) with glass fibers. Thislimited success is attributed to the poor wetting of the glass by thevinyl chloride and poor adhesion between the glass and the poly(vinylchloride) matrix.

A need exists for a process for the preparation of glass con' centratecapsules which would provide a high concentration of glass fibers invery compact form which capsules approximate the size and shape of theresin matrix with which they are blended prior to any extruding ormolding operations. Moreover, a need exists for glass concentrates incapsule from which would not be susceptible to the problems ofdebundling, haystacking and matting of glass fibers, etc. which commonlyoccur when using the glass strands of the prior art. Furthermore, adefinite need exists for a more economical way to prepare poly(vinylchloride) glass composites with improved physical properties.

SUMMARY OF THE INVENTION THe present invention solves the problems andfulfills the needs mentioned above by providing a process for thepreparation of capsules which contain a high concentration of glassstrands in a collimated array within a poly(vinyl chloride) matrix. Inthe capsules which are prepared according to the processes of thisinvention, the individual microfibers in the strands are also coatedwith poly(vinyl chloride). These capsules can be prepared in varioussizes and shapes by controlling the reaction conditions in order todecrease the problem of segregation. This causes a significant reductionin the need for the elaborate precautions heretofore used in the priorart in order to ensure a uniform and constant feed rate of glass andresin to the processing machinery. Furthermore, the problems ofdebundling, haystacking and matting of glass fibers which wereheretofore commonly associated with the glass strands of the prior artare virtually eliminated. Moreover, the glass concentrate capsules ofthe present invention can be used to prepare poly(vinyl chloride)-glasscomposites with improved physical properties such as lower waterabsorption, higher impact strength, higher tensile strength, highermodulus, improved elongation and heat distortion properties.Furthermore, these improved properties are obtained through a moreeconomical process.

DESCRIPIlON OF THE DRAWINGS NO. I shows a typical glass strand whichcomprises a bundie of microfibers bound together by a sizing agent.

FIG. 2 shows a typical assembly of glass strands of the prior art whichis prepared by coating a vinyl aromatic polymer onto a plurality ofendless glass strands and then cutting the resulting coated assembly ofstrands to the desired length. Note that the ends of the microfibers areexposed providing sites for debundling.

FIG. 3 illustrates encapsulated single strands of the prior art wherethe glass strand is saturated with monomer which is then polymerized insitu.

FIG. 4 is a plan view of a glass concentrate of the present invention.

FIG. 4A is a front view of the capsule shown in FIG. 4 with the top ofthe capsule cut away to expose the ends of the glass strands. Note thatthe glass strands are aligned in a collimated array which allows a veryclose packing of the strands to provide a high concentration of glasswithin the capsule.

FIG. is a plan of another type of glass-concentrate capsule preparedaccording to the present invention.

FIG. 5A is a top view of the capsule shown in FIG. 5. In this view thetop has been cut away to expose the ends of the glass strands. Onceagain note that the glass strands are aligned in a collimated arraywhich allows a very close packing of the strands to provide a highconcentration of glass within the capsule.

FIG. 6 is a plan view of another type of glass-concentrate capsule whichis prepared according to the processes of the present invention. Thisparticular configuration is in the form of a flat tape as opposed to therounded capsules illustrated in FIGS. 4A and 5A.

FIG. 6A is a top view of the capsule shown in FIG. 6. Once again notethat the glass strands are aligned in a collimated array which allows avery close packing of the strands to provide a high concentration ofglass within the capsule.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The glass-concentrate capsulesof the present invention are prepared by encapsulating the glass strandsin a resin matrix by in situ polymerization of the monomers using acritical amount of protective colloid and a critical type of agitation.

in the practice of the present invention from to 90 parts by weight ofvinyl chloride monomer are polymerized in the presence of from l0 to 80parts by weight of glass strands, based on 100 parts by weight of glassand monomer. The polymerization is carried out in aqueous suspensionusing a critical amount ofa protective colloid.

The amount of water used will vary of from l00 to 1,600 parts by weight,based on lOO parts by weight total of the glass and monomer. The amountof protective colloid used is critical and must be determined for eachsystem. In general, the amount of the protective colloid used will fallin the range of from 0.05 to 2.0 parts by weight based on l00 parts byweight total of glass and monomer.

The monomer is then polymerized by heating the contents of the vessel toa temperature in the range of from 0 to l l0 C. During this timelow-shear agitation is maintained in order to keep the whole mass movingwhile avoiding localized high shear agitation.

During the polymerization step the glass strands become impregnated andcoated with monomer, aligned and subsequently encapsulated by theresulting resin matrix. The glass fibers in the capsules are normallyaligned in a substantially collimated array to form cylinders or flattapes in which the glass strands are butted end to end. The length ofthe capsules is generally slightly greater than the length of theoriginal chopped strands. The microfibers which form the glass strandsare also surrounded by and imbedded in the polymer matrix.

The glass component used in the present invention are strands of glassfibers which vary in length from 1/32-inch to 34-inch or longer.Preferably, the glass strands are about riainch to l 4-inch long andabout l/l6to 3/l6-inch wide. The glass strands are preferably sized withmaterial which will become swollen in the monomers used to form theresin matrix without dissolving in the matrix. Moreover, the monomersand the polymers formed therefrom should be compatible with the sizeused in order to ensure that the polymers will have sufficient adhesionto the glass strands.

The monomer used in the present invention is vinyl chloride. Optionally,small amounts of a comonomer are used. The preferred comonomers areethylene, propylene, vinyl chloride, maleate and fumarate esters andmonomers of the general formula:

wherein R, is selected from the group comprising hydrogen, alkyl groupsof from one to 10 carbon atoms, aryl groups of from six to 10 carbonatoms including the carbon atoms in ring-substituted alkyl substituents;e.g., vinyl formate, vinyl acetate, vinyl propionate, vinyl benzoate,and the like.

In addition, the present invention also contemplates the use of asaturated rubber component in combination with the foregoing monomers.This rubbery component would include polyisoprene, polyisobutylene,chlorinated polyethylene, ethylene vinyl acetate copolymers, propyleneoxide rubbers, etc. These would include polyblends, graft copolymers andphysical admixtures of a rubbery component with the monomers used toencapsulate the glass. Rubbery composi tions are well known to thoseskilled in the polymer art and need no further explanation here. Also,the glass strands used in the practice of the present invention canfirst be impregnated with a rubber and then encapsulated.

The glass strands may be first wet with either monomer or water. Whenthe strands are first wet with water the monomer will subsequentlydisplace the water and impregnate the glass strands and encapsulate theindividual microfibers as well as the strands themselves. Thus,following polymerization, the individual microfibers as well as thealigned strands are fully sur rounded and protected by the resin matrix.Moreover, by con trolling the polymerization conditions theglass-concentrate capsules can be prepared in a variety of sizes andshapes.

The role of the protective colloid in this invention is very importantand certain critical requirements must be met. The choice of protectivecolloid and the amount used depends on factors such as the length ofglass strands, the monomers used for encapsulation, the ratio of glassto monomers and the ratio of water to monomers. The optimum amount ofprotective colloid is dictated by the size, shape and uniformity desiredin the resulting glass-concentrate capsule.

In general, when excessive protective colloid is used there is noaligning of the glass strands into a collimated array and only a thincoating of polymer is found on the individual strands. Most of thepolymer will be present as fine suspension beads or powders. Wheninsufficient protective colloid is used there is no aligning of glassstrands into a collimated array. Moreover, the polymer forms intoovcrsized beads or else complete coagulation occurs. When using anoptimum amount of protective colloid, the glass strands are individuallycoated with polymer and are aligned and butted endJo-end in asubstantially collimated array to form capsules which pass through anumber 2.5 U.S. standard screen and are retained on number 40 screen.Moreover, when using optimum amounts of protective colloid there arelittle or no polymer fines which indicate that substantially all of themonomer is polymerized around the glass strands.

Examples of protective colloids for use in the present invention includethose synthetic and naturally occurring material which are welt known tothose skilled in the art. These include polyvinyl alcohol, partiallyhydrolyzed polyvinyl acetate, soluble starch, soluble starchderivatives, dextrin, gum tragacanth, gum arabic, gum acacia, gumtragon, gelatin, agar agar, methyl cellulose, methylhydroxypropylcellulose, ethylhydroxyethyl cellulose, sodium carboxymethyl cellulose,water-soluble glycol cellulose, bentonite, sodium alginate, sodiumsilicate, tricalcium phosphate, salts of polyearboxylic acids such asthe sodium salts of polyacrylic acId, partial esters of polymethacrylicacid, copolymers of acrylic acid and 2- ethyl hexyl acrylate copolymersof vinyl acetate and maleic anhydride and the like.

Especially preferred protective colloids include polyvinyl alcohol,partially hydrolyzed polyvinyl acetate, bentonite, par tial esters ofpolymethacrylic acid and copolymers of acrylic acid and 2-ethyl hexylacrylate which are described in US. Pat. No. 2,945,013 and copolymers ofvinyl acetate-maleic anhydride.

The amount of protective colloid used is very critical and must bedetermined for each individual system. The amount of protective colloidused will vary with the nature of the colloid as well as with the amountof glass. monomer and water used in the polymerization step. The lengthof the glass strands and the type of monomers are other factors whichdetermine the amount of protective colloid used. In this regard itshould be noted that larger concentrations of suspending agents arerequired with longer glass strands and with decreasing monomer/glassratio.

As a general rule, the amount of protective colloid used will be in therange of from 0.05 to 2.0 percent by weight based on the total weight ofmonomer and glass. Within this range the optimum amount for a givensystem must be determined by the nature of the other components in thesystem as well as by the amounts of these components. Those skilled inthe art will be readily able to determine the optimum amount ofprotective colloid required for any given system from the teachings setforth in the working examples.

The amount of water used in the polymerization process will varydepending on the weight of the glass and monomers. In general. theamount of water will vary from 100 to L600 parts by weight. based on 100parts by weight of the glass and monomer. in the especially preferredprocess. where the monomer is present in amounts of from 40 to 80 partsby weight based on a total of 100 parts by weight of glass and monomer.the amount of water used will vary from 100 to 600 parts by weight basedon a total of 100 parts by weight of glass and monomer.

The type of agitation used during the polymerization of the monomers isalso very critical. Collimation and encapsulation of the fibers is onlysuccessfully achieved when using lowshear agitation of the type thatcauses the whole mass to move without causing localized high-shearagitation. Attempts to encapsulate glass fibers in an agitatedPfaudler-type reactor generally results in considerable debundling ofthe glass strands into the fibers which tended to form matted ballswhich interferes with the collimation. Suitable agitation may beachieved by tumbling the reactor end-toend, or in those types ofhorizontal-type reactors where the entire mass is moved in acascading-type motion.

in the preferred polymerization process of this invention, conventionalpolymerization initiators and chain transfer agents are used. However,it should be noted that the use of these materials are optional and thatthe polymerization step may be carried out using heat along without anypolymerization initiator.

The polymerization step is carried out at temperatures of from 0 to l l0C. under pressure. The preferred polymerization temperature is in therange of from 40 TO 90 C. The polymerization step is carried out until asubstantial amount of monomer is converted to polymer. The time requiredwill de' pend on the particular system and polymerization conditionsused as well as on the degree of conversion desired.

The glass-concentrate capsules of the present invention comprise from to80 percent by weight of glass. More preferably. the capsules comprisefrom to 70 percent by weight of glass. Conversely. the capsules comprisefrom 20 to 90 percent by weight of thermoplastic resin matrix. Morepreferably. the capsules comprise from 30 to 80 percent by weight ofresin.

The preferred glass-concentrate capsules of the present invention arethose which pass through a number 2.5 US. stan dard screen and which areretained on a number 40 US. standard screen. The more-preferredglass-concentrate capsules are those that pass through a number 4 screenand which are retained on a number 20 screen.

The glass-concentrate capsules weigh about 10 to 350 times more than theaverage weight of one of the original glass strands used as the startingmaterial. The preferred glass-concentrate capsules weigh about 20 to 150times more than the average weight of one of the original glass strands.

Preferably, at least tive to 10 glass strands are encapsulated in theglass-concentrate capsules of the present invention. As stated above.these are encapsulated in a substantially collimuterl array within itthermoplastic matrix. The substantially collimated array allows closepacking of the glass strands which, in turn, provides a capsule with ahigh concentration of glass.

The final size. shape and composition of the glass-concentrate capsuleswill depend on the particular system and polymerization conditions used.These will be dictated by the particular end use requirements desired.In general. the capsules are prepared so that they can be blended with adiluent thermoplastic matrix in the form of powder. beads or extrudedchips. without encountering problems of segregation or nonuniformity.

The following examples are set forth in illustration of this inventionand should not be construed as a limitation thereof. Unless otherwiseindicated, all pans and percentages given are by weight.

EXAMPLE 1 This example illustrates the preparation of glass-concentratecapsules which contain about 30 percent by weight of glass strandsarranged in a collimated array within a vinyl chloride polymer matrix.The following charge is used in this example:

Ingredients Parts by weight chopped-glass strands l6-inch lung vinylchloride water methyl cellulose lauroyl peroxide The chopped glassstrands (Johns-Manville CS-308) are charged to a reactor and theentrapped air is removed by pu rging with nitrogen. The vinyl chloridemonomer is then charged to the reactor under a nitrogen purge. Thereactor is then sealed and rotated to completely wet the glass withmonomer. After the glass is completely wet by the monomer. nitrogenpurged. distilled water is charged along with the methyl cellulose. Themethyl cellulose used as the protective colloid is a hydroxypropylmethylcellulose ether. which is available as Methocel 90 HO. This materialwhich has a viscosity of about 4.000 c.p.s. is prepared byetherification of from to pe rcent of the available cellulose hydroxylgroups with methyl and hydroxy propyl groups. The reactor is then sealedand rotated end-over-end in a thermostatically controlled water bath at54 C. for 16 hours. The resulting capsules are then discharged onto ascreen and washed with cold and hot water. There is only slight evidenceof polymer agglomeration and there are only a few fine polymer particlesindicating that most of the monomer has polymerized around the glassfibers.

The resulting glass concentrate capsules which contain about 30 percentby weight of glass. pass through a 2.5 U.S. standard screen and areretained on a 40 screen. These capsules weigh l0 to 30 times more thanthe average weight of the /e-int:h glass strands which are used as thestarting material. Examination of a cross section of representativecapsules shows a plurality of glass strands in a substantiallycollimated array wherein the microfibers in the strands are alsoencapsulated by polymer.

Other representative capsules are heated in a muffle fur nace in orderto burn off the polymer exposing a plurality of glass strands in asubstantially collimated array.

EXAMPLE 2 Example I is repeated here except that the amount of methylcellulose is reduced to 0.l2 part. The resulting glassconcentratecapsules are comparable to those obtained in example 1.

EXAMPLE 3 Example 2 is repeated here except that the amount of methylcellulose is increased to 0.24 part. The resulting glassconcentratecapsules are comparable to those obtained in cxample 2.

EXAMPLE 4 This example illustrates that collimation of the glass strandsdoes not occur when the amount of the methyl cellulose protectivecolloid used in examples 1 to 3 falls below a certain critical level.

Example 1 is repeated here except that the amount of protective colloidis reduced to 0.04 part. During the course of the polymerizationreaction agglomeration of monomerpolymer occurs and no glass-concentratecapsules are obtained.

EXAMPLE 5 EXAMPLE 6 This example illustrates the prewetting of the glasswith water followed by charging of the monomer to the reaction vessel.

Example 1 is repeated here except that the glass strands are first wetwith water followed by charging of the monomers. The resultingglass-concentrate capsules are comparable to those obtained in example1, except that the glass content is about 27 percent by weight.

EXAMPLE 7 Example 6 is repeated here except that 0.10 part of methylcellulose is used. The resulting glass-concentrate capsules arecomparable to those obtained in example 6.

EXAMPLE 8 Example 6 is repeated here except that 0.28 part of methylcellulose is used. The resulting glass-concentrate capsules arecomparable to those obtained in example 6.

EXAMPLE 9 This example is set forth to illustrate the preparation ofglass-concentrate capsules containing about 43 percent by weight ofglass. The following charge is used:

Ingredients Parts by weight chopped-glass strands it-inch long 25 vinylchloride 40 water 120 methyl cellulose 0.30 lauroyl peroxide 012 Thegeneral polymerization procedure of example I is repeated here exceptthat the vinyl chloride monomer is charged after the glass has been wctwith'the water. The resulting capsules are then discharged onto a screenand washed with cold and hot water. There is only slight evidence ofpolymer agglomeration and there are only a few fine polymer particlesindicating that most of the monomer has polymerized around the glassfibers.

The resulting glass concentrate capsules which contain about 43 percentby weight of glass. pass through a 4.0 US.

standard screen and are retained on a 20 screen. These capsules weighIt) to 30 times more than the average weight of the lit-inch glassstrands which are used as the starting material. Examination of a crosssection of representative capsules shows a plurality of glass strands ina substantially collimated array wherein the microfibers in the strandsare also encapsulated by polymer.

Other representative capsules are heated in a muffle furnace in order toburn off the polymer exposing a plurality of glass strands in asubstantially collimated array.

Examples ID to l4, which are tabulated in the following table 1, are setforth to illustrate some of the variations in the reactor charge whichare possible within the scope of this invention. In each example thegeneral polymerization methods of example 1 are used and 0.3 percent byweight, based on the weight of the monomer, of lauroyl peroxide, is usedas the polymerization initiator. The encapsulated glass productsobtained in each example are comparable to those obtained in example I.

TABLE L(SUMMARY OF EXAMPgIIgIS 1U T014] (HARGE 'It) REACT ExampleIngredients (parts by weight) 10 ll 12 l3 14 Glass 15 Vinyl chlorideVinyl acetate NOTE.Col1oid A=a copolyrner of vinyl acetate and mulolcanhydridl- (1/1 mole ratio); Colloid B=polyvinyl alcohol havin aresidual vinyl acetate content of 30% by weight and a 4% aqueoussolution viscosity at 20 C. of 21 cps; Colloid (I =a copolymi-r of vinylmethyl ether and maleic anhydride (1ft mole ratio); Colloid -the methylcellulose used in Example A.

EXAMPLE l5 This example illustrates the preparation of glass-concentratecapsules which contain about 30 percent by weight of A inch glassstrands arranged in a collimated array within a poly(vinyl chloride)matrix. The following charge is used in this example:

The protective colloid and the general procedures of example l are usedin this example.

The resulting glass concentrate capsules which contain about 32 percentby weight of glass. pass through a 2.5 [1.5. standard screen and areretained on a 40 screen. These capsules weigh 10 to 35 times more thanthe average weight of the Vrinch glass strands which are used as thestarting material. Examination of a cross section of representativecapsules shows a plurality of glass strands in a substantiallycollimated array wherein the microfibers in the strands are alsoencapsulated by polymer.

Other representative capsules are heated in a mul'fle furnace in orderto burn off the polymer exposing a plurality of glass strands in asubstantially collimated array.

The following examples 16 to 24 illustrate the critical requirement ofusing lowshear agitation wherein the whole suspension polymerizationmass moves while avoiding localized higheshear agitation. The apparatusused in these examples is conventional for suspension polymerization andis well known to those skilled in the art. Here the polymerizationreaction is carried out in an autoclave equipped with a /16- inch steeltherrnowell baffle, an agitator and a nitrogen inlet. Both anchor andPfaudler-type agitator blades are used in these examples. Except for thedifferences in the reactors, the general polymerization procedures usedabove are followed here.

EXAMPLES l6 to 18 In these examples the methyl cellulose used in exampleI is used as the protective colloid. The agitator used is a flat-facedanchor agitator having a diameter of 3% inches and a )-inch face. Thoseskilled in the art will readily recognize this agitator as being of atype conventionally used in polymerization reactions. The agitator isrun at 200 r.p.m. which is determined to be optimum in order to preventdebundling of the glass strands. However, at this speed there isinsufficient turbulence and the glass could not adequately be dispersed.Consequently, there is no encapsulation and collimation of the glass. Asummary of the charges used in these examples is set forth in table I 1.

TABLE ll Summary of Examples 16 to 18 Example Ingredients [Parts byweight) 16 17 I8 glass strands ii-inch long l5 l5 vinyl chloride 40 4040 water H0 110 200 methyl cellulose 0. l 8 0.20 0.24

luuruyl peroxide 0.12 0.12 0.]!

The foregoing examples 16 to 18 are repeated except that a 3%-inchdiameter anchor agitator having curved l-inch wide blades with a slighttwist reaching to the top of the liquid is used. Once again an agitatorspeed of 200 r.p.m. was determined to be optimum to prevent debundlingof the glass strands. No improvement in dispersing the monomer/glassslurry is observed and there is no encapsulation and collimation of theglass.

EXAMPLES l9 to 2] EXAMPLES 22 to 24 In these examples the generalprocedures of examples 16 to 18 are repeated except that a Pfaudler-typeagitator which is 3 inches in diameter is used. The agitator is athree-fingered retreating blade type with blades )(s-inch wide. Theslurry is adequately dispersed without excessive shearing of the glassstrands by placing the retreating blades close to the bottom of thereactor, and running the agitator in the range of from 220-550 r.p.m.Examination of the resulting product from each example indicates thatthere is some coating of some of the individual glass strands. However,no collimation is observed to take place. There is also substantialamounts of matted glass balls and finely dispersed polymer.

The use of conventional suspension polymerization equipment andprocedures causes shearing and debundling of the glass fibers. Theresulting matted glass balls are especially un desirable as they causedisruption of the system. Moreover, collimation of the glass strandsdoes not occur when using conventional suspension-type polymerization.Successful collimation is only found to occur with lowshear agitation ofthe type which causes the whole suspension polymerization mass to movewhile avoiding localized high-shear agitation. Examples of suitable-typeagitation include the cascading type of agitation that occurs when thereactor is tumbled end-overend as in example 1 and that which occurs inliquid-solid blenders, conical blenders and horizontal-type reactors.These reactors are well known to those skilled in the art and need nofurther description here.

The glass-concentrate capsules of the present invention are blended witha thermoplastic resin matrix and then processed into useful composites.The use of the glass-concentrate capsules of the present inventionprovides a more convenient and more economical process for preparingcomposites than other methods previously used in the prior art.Moreover, the physi cal properties of the composites prepared from theglass-con centrate capsules of the present invention are superior inmany respects to the properties of those composites prepared accordingto the procedures of the prior art. The improved properties which areobtained in the final composite include lower water absorption. highertensile and impact strength, higher modulus and better elongation.

The following examples are set forth in order to illustrate the improvedproperties of composites which are prepared from the glass-concentratecapsules of the present invention.

In these examples the composites are prepared by mixing the glassconcentrate capsules, or the glass strands in case of the controlexamples, with a thermoplastic resin matrix. The proportions ofingredients in each example are adjusted so as to provide compositescontaining approximately 20 percent by weight of glass. The blendedingredients are extruded on a l-inch extruder using a single-flightvinyl screw having a length to diameter (L/D0 ratio of 18. theextrusions are carried out at temperatures of 400 F. while cooling thehopper with water. Tl-le extrudiate is air colled on a long takeofftable and chopped into %-inch to ii-inch chips in a standard doubleblade cutter. All of the test specimens are prepared using 1 percent byweight of Acrawax C lubricant and 1.25 percent by weight of a tinstabilizer. The POLY(vinyl chloride) used in each example is ahomopolymer having a weight average molecular weight in the range offrom 50,000 to 58,000.

Test specimens are injection molded at 370 F. and 700 to 1,000 p.s.i.using an oversized orifice in the nozzle. The test specimens are thensubjected to the following tests:

tensile PROPERTIES TEst specimens (4 inches XVe inch Xl/IO inch) areprepared by injection molding at 370 F. and 1,000 p.s.i. Tensile moduli,fail strength and elongation are determined on a floor-mcdel instronusing an extensometer.

IZOD IMPACT Test specimens (2 A inches X inch X 16 inch) are moldedunder similar conditions to the tensile specimens except that 700 p.s.i.pressure is used. The specimens are notched with a k 0.l inch notchradius and impact strength is determined using a 2-lb. hammer.

HEAT DlSTORTlON Heat distortion is determined on injection molded 2 Viinches XV: inch inch samples at 264 p.s.i., with a 2 inches span.

EXAMPLE 23 (CONTROL) This example is set forth as a control toillustrate the properties of poly(vinyl chloride) test specimens whichcontain no glass-reinforcing AGENT. The test specimens are preparedaccording to the above procedures. Test results are tabulated in tableI]! below.

EXAMPLE 24 (CONTROL) Example 23 is repeated here except that percent byweight of the poly(vinyl chloride) is replaced by astyrene/acrylonitrile copolymer which contains 74 weight percent styreneand 20 weight percent acrylonitrile. This example is included as acontrol to illustrate that the presence of poly(styrene-acrylonitrile)upgrades the physical properties of the poly(vinyl chloride).

EXAMPLE 25 This example is set forth to illustrate the properties of acomposite which is prepared according to the teachings of the prior art.In this example plain glass strands of the type illustrated in FIG. Iare dry blended with poly(vinyl chloride) homopolymer. Specialprecautions were taken to ensure proportionate feeding to the extruderin order to avoid the severe problems of glass segregation.nonuniformity of glass distribu tion, glass debundling during transferand blending and briding of glass in the feed hoppers. Composites areformed and tested according to the above procedures. The test resultsare tabulated in the table Ill below EXAMPLE 26 Example 25 is repeatedhere except that about 20 percent of the poly(vinyl chloride) isreplaced by the styrene/acrylonitrile copolymer used in example 24. Thisex ample is set forth in order to further illustrate the superiorphysical properties that are obtained in composites prepared using theglass-concentrate capsules of the present invention.

EXAMPLE 27 In this example the glass concentrate capsules prepared inexample 1 above are blended with the poly(vinyl chloride) homopolymer.Composites are formed and tested according to the above procedures. Thetest results are tabulated in the table [II below.

EXAMPLE 28 Example 27 is repeated here except using theglass-concentrate capsules prepared in example 9. Composites are formedand tested according to the above procedures. The test results aretabulated in the table Ill below.

styrene/acrylonitrile copolymer is blended with the poly(vinyl chloride)there is a slight increase in tensile. modulus and heat distortion whichis accompanied by a decrease in percent elongation and izod impact.However. the physical properties of this polyblend are still inferior tothe glass-reinforced polymers.

Examples 25 and 26 are prepared by the conventional prior art method ofdry blending glass strands and the resin matrix. These glass-reinforcedexamples have superior physical properties to the unreinforced samplesin examples 23 and 24 except for percent elongation. Note once againthat substitution of a styrene/acrylonitrile copolymer for part of thepoly(vinyl chloride) gives rise to a difference in some of the physicalproperties. In this regard note that example 26 has slightly bettertensile and heat distortion than the corresponding example 25 which doesnot contain a styrene-acrylonitrile copolymer. However, the propertiesof these samples are still inferior to those samples prepared from theglass'concentrate capsules of the present invention.

Examples 27 and 28. which are prepared using the glassconcentratecapsules of the present invention. are definitely superior in tensile,modulus, heat distortion and izod impact to those samples which do notcontain any glass reinforcing ele ment (examples 23 and 24). Examples 27and 28 are also superior to examples 25 and 26, the glass-reinforcedcomposites prepared by the dry-blending procedure of the prior art. inregard to tensile, percent elongation. modulus and izod impact.

The superior tensile, modulus and izod impact results which are obtainedusing the glass-concentrate capsules of the present invention (examples27 and 28) are surprising in view of the fact that prior attempts toreinforce poly( vinyl chloride) with glass have been met withconsiderable difiiculty. Consequently, it was believed that the physicalproperties of poly( vinyl chloride) could not be upgraded to the sameextent by glass fibers as the styrene homopolymers and copolymers.Poly(vinyl chloride) presented a problem in that the adhesion betweenthe poly(vinyl chloride) and the glass was less than desirable.Furthermore, it was believed that the processing conditions required forpoly(vinyl chloride )lglass composites caused abrasion and subsequentdegradation of the glass fibers. Consequently, the glass fibers lostmuch of their rein forceability during the processing step.

The glass-concentrate capsules of the present invention go a long way tosolving the foregoing problems. In the present invention there is betterwetting of the glass by the monomer. This leads to better adhesion ofthe poly(vinyl chloride) matrix to the glass and subsequentencapsulation of the in dividual fibers within the glass strands whichare all encapsul The composite! in Examples 23 and 24 are controlsamples which contain no glass. The composites in Examples 25 and 2B areprepared by the prior art. un-tliod of dry blending glass strands andthe thermoplastic polymer matrix. The composites in Examples 27 and 28are prepared using the glass concentrate capsules of the presentinventionv The data in the foregoing table lIl clearly illustrate thatcomposites prepared from the glass-concentrate capsules of the presentinvention (examples 27 and 28) have generally superior physicalproperties than the control samples (examples 23 and 24) or thosecomposites prepared according to the teaching of the prior art (examples25 and 26).

Except for percent elongation. the unreinforced polymers of examples 23and 24 have poorer physical properties than those reinforced samples. lnexample lated with poly(vinyl chloride) and arranged in a collimatedarray.

ln addition to the foregoing tests, water absor tion test are run oncomposite tensile samples by soaking the composite in water at 65 C. for24 hours. After this time the sample is examined visually, the amount ofwater pickup is measured. and a tensile test is run on the wet sample.The test samples from examples 27 and 28, which are prepared using theglass-con- 24, when a centrate capsules of the present invention. showless opaqueness, less water pickup and higher wet tensile strength thando the test samples from the other examples.

lt would appear that the poorer water absorption test results that wereobtained in examples 25 and 26 are due to water wicking in along theglass fibers in the composite causing separation of the matrix from theglass with resulting numerous microcracks which causes opaqueness in thecomposite. Consequently, these composites absorb more water, exhibitmore opaqueness and exhibit a greater decrease in tensile strength thanthose composites which are prepared from the glass-concentrate capsulesof the present invention. In the glass-concentrate capsules of thepresent invention the individual strands and the microfibers making upthe strands are encapsulated by the polymeric matrix. Thus, there isless wicking of water by the glass fibers, less water absorption, lessopaquencss and greater retention of tensile strength. Moreover, it isobserved. after burning off the resin matrix. that the glass fibers fromthe glass-concentrate capsules of the present invention show far lessfiber abrasion or damage due to mechanical processing in the extrudingand molding operation. On the other hand, there is much greater fiberabrasion and damage in those composites which are prepared in examples25 and 26. Presumably, the polymeric coating around the individualmicrofibers and glass strands in the glass concentrate capsules of thepresent invention protects the fibers from damage and abrasion duringmechanical processing of these materials. Consequently, the fibers arebetter able to reinforce the resulting composite thus giving it greaterstrength.

The foregoing theory in regard to the better properties of compositesmade from the glass-concentrate capsules of the present invention is setforth to explain the observed effects and is not intended that the scopeof the invention should, in any way, be limited by this theory.

The composites which are prepared from the glass concentrate capsules ofthe present invention are especially useful in the fabrication of moldedand extruded parts for automobiles such as dashboards, moldings, trim,etc. refrigerators, radio and television cabinets. Other uses for thesecomposites are found in household appliances, industrial applicationsand in general wherever high performance thermoplastic resin parts arerequired.

It will be obvious to those skilled in the art that many modificationsmay be made in the products and processes set forth above withoutdeparting from the scope of this invention.

What is claimed is:

l. A process for the preparation of glass-concentrate capsuleu whichcomprise a plurality of strands of glass fibers en cupsulatcd in acollimated array within a vinyl chloride polymer matrix which processcomprises:

A. Forming a suspension of strands of glass fibers in a vinyl chloridemonomer/water mixture containing from 0.05 to 2.0 percent by weight ofprotective colloid based on the total weight of monomer and glass;

B. Agitating the suspension using a low-shear type of agitation whichmoves the whole suspension mass while avoiding localized high-shearagitation;

C. Polymerizing the monomer; and

D. Recovering the glass-concentrate capsules.

2. A process as in claim 1 wherein the glass strands are from A to%-inch long.

3. A process as in claim 1 wherein the monomer is a mixture of vinylchloride and vinyl acetate.

4. A process as in claim 1 wherein the suspension is agitated bytumbling end-over-end.

5. A process for the preparation of glass-concentrate capsules, whichcomprises a plurality of strands of glass fibers encapsulated in acollimated array within a vinyl chloride polymer matrix, which processcomprises:

A. Forming a suspension of strands of glass fibers having a length offrom l/32 to inch in a vinyl chloride monomer/water mixture containingfrom 0.05 to 2.0 percent by weight, based on the total weight of monomerand glass, of a protective colloid selected from the group con sistingof interpolymers of acrylic acid and Z-ethylhexyl acrylate, methylcellulose and polyvinyl alcohol;

B. agitating the suspension using a low-shear type of agitation whichmoves the whole suspension mass while avoiding localized high-shearagitation;

C. polymerizing the monomer; and

D. recovering the resulting concentrate capsules.

6. A process as in claim 5 wherein the glass strands have a length offrom A; to V4 inch.

7. A process as in claim 5 wherein the monomer is a mixture of vinylchloride and vinyl acetate.

8. A process as in claim 5 wherein the protective colloid is methylcellulose.

9. A process as in claim 5 wherein the protective colloid is pollyvinylalcohol.

0. A process for the preparation of glass-concentrate capsules, whichcomprises a plurality of strands of glass fibers encapsulated in acollimated array within a poly(vinyl chloride) matrix, which processcomprises:

A. Suspending from 10 to parts by weight of strands of glass fibershaving a length of from 1/32 to )6 inch in a mixture comprising from 20to parts by weight of vinyl chloride and from [00 to L600 parts byweight of water, based on I00 parts by weight total of glass andmonomer. wherein the water contains of from 0.05 to 2.0 parts by weight,based on I00 parts by weight total of glass and monomer, of methylcellulose;

B. Agitating the suspension by tumbling the suspension masscnd-ovcr-end;

C. Polymerizing the monomer; and

D. Recovering the resulting glass-concentrate capsules.

H. A process as in claim 10 wherein the glass strands have a length offrom about A; to about V4 inch.

[2. A process as in claim 10 wherein the amount of monomer is in therange of from 30 to 80 parts and the amount of water is in the range offrom to 600 parts.

1. FORMING A SUSPENSION OF STRANDS OF GLASS FIBERS IN A VINYL CHLORIDEMONOMER/WATER MIXTURE CONTAINING A CRITICAL AMOUNT (VIZ., FROM 0.05 TO2.0 PERCENT BY WEIGHT BASED ON THE TOTAL WEIGHT OF MONOMER AND GLASS) OFPROTECTIVE COLLOID;
 2. AGITATING THE SUSPENSION USING A LOW-SHEAR TYPEOF AGITATION WHICH MOVES THE WHOLE SUSPENSION PASS WHILE AVOIDINGLOCALIZED HIGH-SHEAR AGITATION;
 2. A process as in claim 1 wherein theglass strands are from 1/8 to 1/4 -inch long.
 3. A process as in claim 1wherein the monomer is a mixture of vinyl chloride and vinyl acetate. 3.POLYMERIZING THE MONOMER; AND
 4. RECOVERING THE GLASS-CONCENTRATECAPSULES.
 4. A process as in claim 1 wherein the suspension is agitatedby tumbling end-over-end.
 5. A process for the preparation ofglass-concentrate capsules, which comprises a plurality of strands ofglass fibers encapsulated in a collimated array within a vinyl chloridepolymer matrix, which process comprises: A. Forming a suspension ofstrands of glass fibers having a length of from 1/32 to 3/4 inch in avinyl chloride monomer/water mixture containing from 0.05 to 2.0 percentby weight, based on the total weight of monomer and glass, of aprotective colloid selected from the group consisting of interpolymersof acrylic acid and 2-ethylhexyl acrylate, methyl cellulose andpolyvinyl alcohol; B. agitating the suspension using a low-shear type ofagitation which moves the whole suspension mass while avoiding localizedhigh-shear agitation; C. polymerizing the monomer; and D. recovering theresulting concentrate capsules.
 6. A process as in claim 5 wherein theglass strands have a length of from 1/8 to 1/4 inch.
 7. A process as inclaim 5 wherein the monomer is a mixture of vinyl chloride and vinylacetate.
 8. A process as in claim 5 wherein the protective colloid ismethyl cellulose.
 9. A process as in claim 5 wherein the protectivecolloid is polyvinyl alcohol.
 10. A process for the preparation ofglass-concentrate capsules, which comprises a plurality of strands ofglass fibers encapsulated in a collimated array within a poly(vinylchloride) matrix, which process comprises: A. Suspending from 10 to 80parts by weight of strands of glass fibers having a length of from 1/32to 3/4 inch in a mixture comprising from 20 to 90 parts by weight ofvinyl chloride and from 100 to 1,600 parts by weight of water, based on100 parts by weight total of glass and monomer, wherein the watercontains of from 0.05 to 2.0 parts by weight, based on 100 parts byweight total of glass and monomer, of methyl cellulose; B. Agitating thesuspension by tumbling the suspension mass end-over-end; C. Polymerizingthe monomer; and D. Recovering the resulting glass-concentrate capsules.11. A process as in claim 10 wherein the glass strands have a length offrom about 1/8 to about 1/4 inch.
 12. A process as in claim 10 whereinthe amount of monomer is in the range of from 30 to 80 parts and theamount of water is in the range of from 100 to 600 parts.